Analyzing data that followed people over a five year period, the research has found that moving to a greener area not only improves people's mental health, but that the effect continues long after they have moved.

The findings add to evidence that suggests increasing green spaces in cities -- such as parks and gardens -- could deliver substantial benefits to public health.

The research is one of the first studies to consider the effects of green space over time and has used data from the British Household Panel Survey, a repository of information gathered from questionnaires filled in by households across Great Britain.

Using data from over 1,000 participants, the research team at the University of Exeter Medical School focused on two groups of people: those who moved to greener urban areas, and those who relocated to less green urban areas.

They found that, on average, movers to greener areas experienced an immediate improvement in mental health that was sustained for at least 3 years after they moved. The study also showed that people relocating to a more built up area suffered a drop in mental health. Interestingly this fall occurred before they moved; returning to normal once the move was complete.

The authors adjusted their data to remove effects from other factors likely to affect mental health over time -- such as income, employment and education -- as well as factors related to personality. Lead researcher, Dr Ian Alcock, believes the study's results could have important implications:

"We've shown that individuals who move to greener areas have significant and long-lasting improvements in mental health. These findings are important for urban planners thinking about introducing new green spaces to our towns and cities, suggesting they could provide long term and sustained benefits for local communities."

In 2012 the World Health Organization cited depression as the leading cause of disability worldwide, and this study builds on research that has found natural environments could act as vital resources to improve health and wellbeing.

Yet up until now, scientists have been unsure how these effects vary over time. Co-author of the paper, Dr Mathew White, says this research has provided an important insight into the mechanism:

"We needed to answer important questions about how the effects of green space vary over time. Do people experience a novelty effect, enjoying the new green area after the move, but with the novelty then wearing off? Or do they take time to realise the benefits of their new surroundings as they gradually get to know local parks? What we've found suggests that the mental health benefits of green space are not only immediate, but sustainable over long periods of time."